Hunter Lovins at Green Festival San Francisco; Photo via Jaymi HeimbuchGreen Festival hit San Francisco for the first springtime event. If you haven't hit one of these events yet, you're missing out. From DC to Chicago, from Seattle to San Francisco, Green Festival is the largest event focused on sustainability that you'll likely ever attend. And you'll likely get to see some incredible speakers that rarely ever share a stage. This past weekend, San Francisco saw everyone from Danny Glover to Starhawk get up on stage to talk about the big issues in sustainability. Dozens of speakers lined up to share their thoughts with the thousands of attendees at Green Festival.

Hunter Lovins (shown above) stressed the economic case for moving aggressively to solve such challenges as global warming, peak oil, the vulnerability of our energy infrastructure and others. She talked about the efforts happening right now in businesses and communities to live sustainably, and how it's simply economically smart to make changes, and fast.

Starhawk, one of the most famous voices in environment and spirituality, also stressed ways in which we can, and must, make a very fast transition to sustainable living practices.

Perhaps some of the most household names at the event, Danny Glover and Alice Walker were present, as part of The People Speak LIVE! Tribute to Howard Zinn.

The star-studded line up of speakers went on and on, as Green Festival stressed talks and workshops much more at this event than in the past, showing that doing something green is much more important and complex than simply choosing green products when we're out shopping.